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H Hebert

Publications and source records attributed to H Hebert.

48 records · Page 3Linked to original sources
PubMedDate not supplied

Structure of two-dimensional crystals of membrane-bound Na,K-ATPase as analyzed by correlation averaging.

The structure of two-dimensional crystals of membrane-bound Na,K-ATPase from rabbit kidney has been analyzed with a correlation averaging procedure. Two principally different crystal forms are observed with p1 and p21 symmetry, respectively. In the p1 form the averaged projection structure shows a triangular shaped protein domain interpreted as a protomer (alpha beta-unit) of Na,K-ATPase. In the p21-form the stain-deficient area is extended toward a twofold symmetry axis. The results are in good agreement with a previous analysis where Fourier methods were applied to well ordered crystals of pig kidney Na,K-ATPase and illustrate that the correlation averaging procedure can be used for the analysis of membrane crystals of Na,K-ATPase showing curved lattice lines.

Animals↗
PubMedDate not supplied

Three-dimensional structure of Na,K-ATPase determined from membrane crystals induced by cobalt-tetrammine-ATP.

The three-dimensional structure of Na,K-ATPase has been analyzed with electron microscopy and image processing. The enzyme, purified from pig kidney outer medulla, was arranged in a new form of tetragonal two-dimensional membrane crystals after incubation with cobalt-tetrammine-ATP, a stable MgATP complex analogue. Each continuous protein domain, as delineated by negative stain, consists of two alpha beta-protomers related by a dyad axis. The two rod-like regions are connected by a bridge displaced about 20 A away from the center of the structure toward the lipid bilayer. The domain connecting the two promoters is more constricted and closer to the center of the structure in the Co(NH3)4ATP-induced crystals than in the vanadate-induced p21 crystals. These observations suggest that the difference between previously analyzed dimers of two-dimensional p21 crystals induced with vanadate/magnesium and dimers of p4 crystals induced with Co(NH3)4ATP reflects two different conformational states of the enzyme.

Adenosine Triphosphate↗
PubMedDate not supplied

The three-dimensional structure of trypsin-treated Staphylococcus aureus alpha-toxin.

Trypsin treatment of staphylococcal alpha-toxin cleaves the molecule into two roughly equally sized parts, which results in inactivation of the toxin. Tetragonal arrays of oligomers, closely resembling the native ones, can however be formed on lipid layers. From tilted views of negatively stained crystals a 3D structure to 23 A resolution has been determined by electron microscopy and image processing. On comparison with the 3D structure of the native alpha-toxin (Olofsson et al., J. Mol. Biol. 214, 299-306, 1990) the subdomains are more separated, confirming the differences found when comparing the projection maps (Olofsson et al., J. Struct. Biol. 106, 199-204, 1991). The tryptic cleavage takes place in a postulated hinge region. The results are consistent with the hypothesis that the conformational change required for inducing the membrane permeabilizing property takes place in this region. Furthermore, we present a refined projection map at approximately 10 A resolution based on the analysis of a large number of crystals using unbending methods.

Bacterial Toxins↗
PubMedDate not supplied

[Prognostic histopathological features of malignant melanoma. New statistical approaches (author's transl)].

The records of 203 patients with cutaneous malignant melanoma treated at the Centre René Huguenin, Saint-Cloud, from october, 1959 to december, 1978 were reviewed. Histological data from 155 patients were retained after re-examination. The melanomas, which had previously been classified according to Clark's system of histological type and degree of invasiveness, were re-evaluated according to the thickness, were re-evaluated according to the thickness of the tumour as measured by Breslow's ocular micrometric method. Other histological data, as well as clinical and therapeutic data, were gathered together. One hundred and fifty cases were found to be suitable for standard single and multifactorial analysis, and 96 records contained sufficient information to be analyzed by the new "similarly aggregation" method developed by IBM. Two significant results emerged from the study: the thickness of the tumor is the single most important prognostic factor, as it correlates with the incidence of recurrences, metastases and deaths; by using a small number of clinical and histological variables, it seems possible to draw a profile of every new patient, to classify him in a well-determined prognostic category and, consequently, to institute a complementary treatment when needed.

Female↗